Energy from Sea

These notes are based on the chapter Sources of Energy of class 10 NCERT book and CBSE syllabus.

• Tidal Energy
• Wave Energy
• Ocean Thermal Energy

Tidal Energy

Due to the gravitational pull of the moon, tides happen near seashores. Water rushes up near the seashore during a high tide and goes down during a low tide.

Dams are built near seashores to collect the water which comes during a high tide. When the water runs back to the ocean, the flow of water can be utilized to turn the turbine to generate electricity.

Wave Energy

Waves can also be a good source of energy. Many devices are being designed and tested to produce wave energy.

For example; a hollow tower is built near the seashore. When water gushes in the tube because of wave, it forces the air upwards. The kinetic energy of air in the tube is used to run a turbine. When the wave goes down, air from up goes down the tube which is also used in running the turbine.

Ocean Thermal Energy

Steps of production of ocean thermal energy

• Inside the evaporator, the heat of surface water changes the working fluid into gas.
• Pressurised working fluid into gaseous state runs he turbine, which generates electricity.
• Working fluid is then sent to a condenser where cold deep sea water converts it into liquid state.
• The pump then sends the working liquid into evaporator and the cycle is repeated.

The water at sea surface is hot during daytime, while the water at lower level is cold. The temperature differential in water levels can be utilized to generate energy. If the temperature differential is more than 20°C, then ocean thermal energy can be utilized from that place.

For harnessing ocean thermal energy, a volatile liquid (like ammonia) is boiled using the heat from the warm water at the surface. The steam of the volatile liquid is utilized to run the turbine to generate electricity. Colder water from the surface below is utilized to condense ammonia vapour which is then channelized to the surface to repeat the cycle.

Various methods of harnessing energy from the sea are still at experimental stages. They are yet to become cost effective and hence are not being used for large scale production of energy.